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The Ham class was a class of inshore minesweepers (IMS), known as the Type 1, of the British Royal Navy. The class was designed to operate in the shallow water of rivers and estuaries. All of the ships in the class are named for British place names that end with -"ham". The parent firm that was responsible for supervising construction was Samuel White of Cowes, Isle of Wight.

Quick Facts Class overview, General characteristics ...
HMS Portisham
Class overview
Operators
Built1954–1959
Completed93
General characteristics
TypeMinesweeper
Displacement
  • 120 long tons (122 t) standard
  • 164 long tons (167 t) full load
Length
  • 100 ft (30 m) p/p
  • 106 ft 6 in (32.46 m) o/a, except third sub-group 107 ft 6 in (32.77 m)
Beam
  • 26-group: 21 ft 4 in (6.50 m)
  • 27-group: 22 ft (6.7 m)
Draught
  • 26-group: 5 ft 6 in (1.68 m)
  • 27-group: 5 ft 9 in (1.75 m)
Propulsion
  • 2 shaft Paxman 12YHAXM diesels
  • 1,100 bhp (820 kW)
Speed14 knots (26 km/h; 16 mph)
Range15 tons diesel fuel, ?
Complement2 officers, 13 ratings
Armament1 × Bofors 40 mm L/60 gun or Oerlikon 20 mm cannon
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Description

The class consisted of 93 ships, launched between 1954 and 1959. HMS Inglesham was the first. They were built in three slightly different sub-groups, the first sub-group, the 26-group, is distinguished by pennant numbers 26xx, and the second and third sub-groups, the 27-group, are distinguished by pennant numbers 27xx. The 26-group was of wood and non-ferrous metal composite construction and the 27-group was of all-wood construction. The third sub-group is distinguished by a prominent rubbing strake around the hull and slightly larger dimensions.

Unlike traditional minesweepers, they were not equipped for sweeping moored or magnetic mines. Their work was to locate individual mines and neutralise them. This was a then-new role, and the class was configured for working in the shallow water of rivers, estuaries and shipping channels.

The vessels displaced 164 long tons (167 t) fully laden and were armed with one 40 mm Bofors or 20 mm Oerlikon gun. They were 32.5 metres (107 ft) long overall with a 6.4-metre (21 ft) beam. The construction was of wood to minimise the magnetic signature. The crew complement was 15, rising to 22 in wartime.

The engines of this class were Paxman diesels, some of which were built under licence by Ruston and Hornsby of Lincoln. Each vessel had: two 12YHAXM (intercooled) for main propulsion, rated at 550 bhp (410 kW) at 1,000 rpm, plus one 12YHAZ for pulse generation. Maximum speed was 14 knots (26 km/h; 16 mph) dropping to 9 knots (17 km/h; 10 mph) when mine hunting.

The class shared the same basic hull as the Ley-class minehunter and the Echo-class inshore survey craft.

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Ships

In 1964 Ten of the vessels were allocated to the Royal Naval Auxiliary Service

Name Call sign Pennant No Completed Builders Joined RNXS Disposal
Birdham M.2785 5-Mar-57 J.Taylor 1964 May 1980 - Arrived Great Wakering, Essex for Breaking
Odiham M.2783 27-Jul-56 Vospers 1964 1978 - on disposal list., May 1980 sold to Sutton & Smith, Great Wakering, Essex
Pagham M.2716 22-Mar-56 Jones, Buckie 1964 to 1974.1982, RNR Tender
Portisham GTDG M.2781 26-Mar-56 Dorset Yacht 1964 to 1983 at HMS Vernon, Portsmouth
Puttenham M.2784 9-May-58 Thorneycroft 1964 to 1978 at Plymouth
Saxlingham M.2727 29-Jan-57 Berthon Boat 1964 to 1965. Approved to scrap 1966. 2 May 1968 sold to Ross & Cromarty CC for Lewis Sea School
Shipham MTMW M.2726 3-Feb-56 Brooke Marine 1964 to 1983 at Gillingham
Shrivenham M.2728 11-Aug-56 Bolson 1964 to 1965. For disposal in 1966. Sold to PLA, 21 Feb 1969. Approved to scrap 1966. 2 May 1968 sold to Ross & Cromarty CC for Lewis Sea School
Thakeham GTJC M.2733 15-Nov-57 Fairlee Yacht 1964 to 1978. 1979 for disposal
Tongham M.2735 18-Jun-57 J.Miller 1964 to 1978, also PAS. 1979 for disposal
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References

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